A GREAT TIDAL WAVE.

During the last few days anxious questionings have been heard respecting the next spring tides. A certain naval¹ officer, who conceives that he can trace in the relative positions of the sun and moon the secret of every important change of weather, has described in the columns of a contemporary the threatening significance of the approaching conjunction of the sun and moon. He predicts violent atmospheric² disturbances³; though in another place he tells us merely that the conjunction is to cause ‘unsettled weather,’ a state of matters to which we in England have become tolerably well accustomed.

But people are asking what is the actual relation which is to bring about such terrible events. The matter is very simple. On October 5, the moon will be new—in other words, if it were not for the brightness of the sun, we should see the moon close by that luminary⁵ on the heavens. Thus the sun and moon will pull with combined effect upon the waters of the earth, and so cause what are called spring tides. This, of course, happens at the time of every new moon, but sometimes the moon exerts a more effective pull139 than at other times; and the same happens also in the case of the sun; and on October 5, it happens that both the sun and the moon will give a particularly vigorous haul upon the earth’s waters. As regards the sun, there is nothing unusual. Every October his pull on the ocean is much the same as in preceding Octobers. But October is a month of high solar tides—and for these reasons:—In September, as everyone knows, the sun crosses the equinoctial; and, other things being equal, it would be when on the equinoctial that his power to raise a tidal wave would be greatest. But other things are not equal; for the sun is not always at the same distance from the earth. He is nearest in January; so that he would exert more power in that month than in any other, if his force depended solely⁶ on distance. As matters actually stand, it will be obvious that at some time between September and January the sun’s tidal power would have a maximum value. Thus it is that October is a month of high solar tidal waves.

But it is the lunar wave which will be most effectively strengthened at the next spring tide. If we could watch the lunar tidal wave alone (instead of always finding it combined with the solar wave) we should find it gradually increasing, and then gradually diminishing, in a period of about a lunar month. And we should find that it was always largest when the moon looked largest, and vice⁷ versa. In other words, when the moon is in perigee⁸ the lunar wave is largest. But then there is another consideration. The lunar wave140 would vary according to the moon’s proximity⁹ to the equinoctial; and (other things being equal) would be largest when the moon is exactly opposite the earth’s equator. If the two effects are combined, that is, if the moon happens to be in perigee and on the equinoctial at the same time, then of course we get the largest lunar tidal wave we can possibly have.

Now this ‘largest lunar wave’ occurs at somewhat long intervals¹⁰, because the relation on which it depends is one which is, so to speak, exceptional. Still the relation does recur¹¹, and with a certain degree of regularity¹². When it happens, however, it by no means follows that we have a very high tide; because it may occur when the tides are near ‘neap’; in other words, when the sun and moon exert opposing effects. The largest lunar wave cannot stand the drain which the solar wave exerts upon it at the time of neap tides. Nor would the large lunar tidal wave produce an exceptionally high tide, even though it were not the time of ‘neap,’ or were tolerably near the time of ‘spring’ tides. Only when it happens that a large lunar wave combines fully¹³ with the solar wave, do we get very high tides. And when, in addition to this relation, we have the solar wave nearly at a maximum, we get the highest of all possible tides. This is what will happen, or all but happen, on October 5 next. The combination of circumstances is almost the most effective that can possibly exist.

But, after all, high tides depend very importantly on other considerations than astronomical¹⁴ ones. Most141 of us remember how a predicted high tide some two years ago turned out to be a very moderate, or, if we may use the expression, a very ‘one-horse’ affair indeed, because the winds had not been consulted, and exerted their influence against the astronomers¹⁵. A long succession of winds blowing off-shore would reduce a spring tide to a height scarcely exceeding the ordinary neap. On the other hand, if we should have a long succession of westerly winds from the Atlantic before the approaching high tide, it is certain that a large amount of mischief¹⁶ may be done in some of our riverside regions.10

As for the predicted weather changes, they may be regarded as mere⁴ moonshine. A number of predictions, founded on the motions of the sun and moon, have found a place during many months past in the columns of a contemporary; but there has been no greater agreement between these predictions and the weather actually experienced than anyone could trace between Old Moore’s weather prophecies and recorded weather changes. In other words, there have been certain accordances which would be very remarkable¹⁷ indeed if they did not happen to be associated with as many equally remarkable discordances. Random¹⁸ predictions would be quite as satisfactory.

A very amusing misprint has found its way into many newspapers in connection with the coming tide. It is interesting as serving to show how little is really known by the general public about some of the simplest142 scientific matters. The original statement announced that the sun would not be in perihelion by so many seconds of semi-diameter, in itself a very incorrect mode of expression. Still it was clear that what was meant was, that the earth would be so far from the place of nearest approach to the sun that the latter would not look as large as it possibly can look, by so many seconds of semi-diameter. In many papers, however, we read that the ‘sun will not be in perihelion by so many seconds of mean chronometer¹⁹!’ Who first devised this marvellous reading is unknown.

(From the Daily News for September 27, 1869.)

1 naval   

adj.海军的，军舰的，船的

参考例句：

• He took part in a great naval battle.他参加了一次大海战。
• The harbour is an important naval base.该港是一个重要的海军基地。

2 atmospheric   

adj.大气的，空气的；大气层的；大气所引起的

参考例句：

• Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
• Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。

3 disturbances   

n.骚乱( disturbance的名词复数 )；打扰；困扰；障碍

参考例句：

• The government has set up a commission of inquiry into the disturbances at the prison. 政府成立了一个委员会来调查监狱骚乱事件。
• Extra police were called in to quell the disturbances. 已调集了增援警力来平定骚乱。

4 mere   

adj.纯粹的；仅仅，只不过

参考例句：

• That is a mere repetition of what you said before.那不过是重复了你以前讲的话。
• It's a mere waste of time waiting any longer.再等下去纯粹是浪费时间。

5 luminary   

n.名人，天体

参考例句：

• That luminary gazed earnestly at some papers before him.那个大好佬在用心细看面前的报纸。
• Now that a new light shone upon the horizon,this older luminary paled in the west.现在东方地平线上升起了一轮朝阳，这弯残月就在西边天际失去了光泽。

6 solely   

adv.仅仅，唯一地

参考例句：

• Success should not be measured solely by educational achievement.成功与否不应只用学业成绩来衡量。
• The town depends almost solely on the tourist trade.这座城市几乎完全靠旅游业维持。

7 vice   

n.坏事；恶习；[pl.]台钳，老虎钳；adj.副的

参考例句：

• He guarded himself against vice.他避免染上坏习惯。
• They are sunk in the depth of vice.他们堕入了罪恶的深渊。

8 perigee   

n.近地点

参考例句：

• The Moon reaches its absolute perigee once a year.月球每年有一次达到它的绝对近地点。
• Once the satellite reaches perigee,it will eject a small probe which enter the planet's atmosphere.当人造卫星达到近地点时，就会发射一根小探针，这根探针将进入行星的大气层。

9 proximity   

n.接近，邻近

参考例句：

• Marriages in proximity of blood are forbidden by the law.法律规定禁止近亲结婚。
• Their house is in close proximity to ours.他们的房子很接近我们的。

10 intervals   

n.[军事]间隔( interval的名词复数 )；间隔时间；[数学]区间；（戏剧、电影或音乐会的）幕间休息

参考例句：

• The forecast said there would be sunny intervals and showers. 预报间晴，有阵雨。
• Meetings take place at fortnightly intervals. 每两周开一次会。

11 recur   

vi.复发，重现，再发生

参考例句：

• Economic crises recur periodically.经济危机周期性地发生。
• Of course,many problems recur at various periods.当然，有许多问题会在不同的时期反复提出。

12 regularity   

n.规律性，规则性；匀称，整齐

参考例句：

• The idea is to maintain the regularity of the heartbeat.问题就是要维持心跳的规律性。
• He exercised with a regularity that amazed us.他锻炼的规律程度令我们非常惊讶。

13 fully   

adv.完全地，全部地，彻底地；充分地

参考例句：

• The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气，然后全部呼出。
• They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。

14 astronomical   

adj.天文学的，（数字）极大的

参考例句：

• He was an expert on ancient Chinese astronomical literature.他是研究中国古代天文学文献的专家。
• Houses in the village are selling for astronomical prices.乡村的房价正在飙升。

15 astronomers   

n.天文学者，天文学家( astronomer的名词复数 )

参考例句：

• Astronomers can accurately foretell the date,time,and length of future eclipses. 天文学家能精确地预告未来日食月食的日期、时刻和时长。 来自《简明英汉词典》
• Astronomers used to ask why only Saturn has rings. 天文学家们过去一直感到奇怪，为什么只有土星有光环。 来自《简明英汉词典》

16 mischief   

n.损害，伤害，危害；恶作剧，捣蛋，胡闹

参考例句：

• Nobody took notice of the mischief of the matter. 没有人注意到这件事情所带来的危害。
• He seems to intend mischief.看来他想捣蛋。

17 remarkable   

adj.显著的，异常的，非凡的，值得注意的

参考例句：

• She has made remarkable headway in her writing skills.她在写作技巧方面有了长足进步。
• These cars are remarkable for the quietness of their engines.这些汽车因发动机没有噪音而不同凡响。

18 random   

adj.随机的；任意的；n.偶然的(或随便的)行动

参考例句：

• The list is arranged in a random order.名单排列不分先后。
• On random inspection the meat was found to be bad.经抽查，发现肉变质了。

19 chronometer   

n.精密的计时器

参考例句：

• Murchison followed with his eye the hand of his chronometer.莫奇生的眼睛追随着他的时计的秒针。
• My watch is more expensive because it's a chronometer.我的手表是精密型的，所以要比你的贵。